It is desirable for a wide variety of rubber and plastic articles, such as pneumatic tires, balloons, air springs, gas diaphragms, seals, packaging materials, and the like to exhibit a high level of barrier resistance, such as barrier resistance to gases and liquids. In some cases, such as balloons and pneumatic tires, it is important for the rubber article to prevent the gas from escaping and in other cases, such as gas diaphragms, it is critical for the rubber article to keep gases from leaking through the article. For instance, the desirability for a weather balloon or even a toy balloon to retain the gas with which it is filled is self apparent. It is, of course, also highly desirable for a pneumatic tire to be capable of providing service over longer time intervals without adding additional gas to compensate for leakage. Rubber articles which need enhanced barrier properties frequently include one or more layers of rubber compositions that exhibit good barrier resistance. However, such a layer must also exhibit physical and chemical characteristics which are in accordance with the overall requirements of the rubber article.
Many pneumatic tires, especially pneumatic automobile tires, include an innerliner layer to inhibit the gas used to inflate the tire from escaping. More specifically, pneumatic tires are toroidal, composite structures that are inflated with a pressurized gas, such as air, nitrogen, or helium, to provide weight support, shock absorbance, and traction transmission for a vehicle body. A key factor that affects tire performance is inflation pressure, which needs to be retained at an optimum level during tire operation. Historically, and in some modern tires, inflation pressure was retained through the use of an innertube. In today's tubeless automobile tires, the retention of inflation pressure is achieved by the use of an innerliner which is a thin layer of a rubber composition having a high level of gas barrier resistance which is laminated to the inside of the pneumatic tire. The tire innerliner serves as a barrier layer which helps to inhibit the gas which is used to inflate the tire from escaping and accordingly allows the tire to maintain a proper level of inflation pressure over an extended period of time.
Halobutyl rubbers, such as, bromobutyl rubber and chlorobutyl rubber are typically included in tire innerliners to attain recommended inflation pressures over desired time intervals. In many cases a halobutyl rubber is blended with natural rubber for utilization in tire innerliners. However, bromobutyl rubber and chlorobutyl rubber are expensive materials which add greatly to the cost of materials needed to build a tire. There has accordingly been a long felt need in the tire industry for lower cost innerliner materials or materials with further enhanced gas barrier properties. Such materials would be helpful in addressing the global demand for energy efficient vehicles, reducing carbon dioxide (CO2) emissions and enhancing driving safety. Additional benefits include better tire durability and reduced manufacturing/material cost.